Table 3.
Unadjusted and Adjusted Risk of Arthritis, by Covariates, Behavioral Risk Factor Surveillance System, 2005a
| Characteristic | Unadjusted OR (95% CI) | Adjusted OR (95% CI) |
|---|---|---|
| Sex | ||
| Male | 1 [Reference] | 1 [Reference] |
| Female | 1.6 (1.5-1.6) | 1.5 (1.5-1.6) |
| Age, y | ||
| 18-34 | 1 [Reference] | 1 [Reference] |
| 35-44 | 2.6 (2.5-2.8) | 2.5 (2.4-2.7) |
| 45-54 | 5.6 (5.3-5.9) | 5.2 (4.9-5.5) |
| 55-64 | 10.6 (10.0-11.3) | 9.5 (8.9-10.0) |
| ≥65 | 16.7 (15.7-17.6) | 13.8 (13.0-14.7) |
| Race/Ethnicity | ||
| Non-Hispanic white | 1 [Reference] | 1 [Reference] |
| Non-Hispanic black | 0.9 (0.8-0.9) | 0.8 (0.8-0.9) |
| Hispanic | 0.4 (0.4-0.5) | 0.5 (0.5-0.6) |
| Other | 0.7 (0.6-0.7) | 0.9 (0.8-1.0) |
| Insurance coverage | ||
| Insured | 1 [Reference] | 1 [Reference] |
| Uninsured | 0.5 (0.5-0.5) | 0.8 (0.7-0.8) |
| Body mass index | ||
| Normal (<25.0 kg/m2) | 1 [Reference] | 1 [Reference] |
| Overweight (25.0-29.9 kg/m2) | 1.4 (1.4-1.5) | 1.4 (1.3-1.4) |
| Class I obesity (30.0-34.9 kg/m2) | 2.0 (1.9-2.1) | 1.9 (1.8-2.0) |
| Class II obesity (35.0-39.9 kg/m2) | 2.4 (2.3-2.6) | 2.5 (2.3-2.7) |
| Class III obesity (≥40.0 kg/m2) | 3.1 (2.9-3.4) | 3.3 (3.1-3.6) |
| PA levelb | ||
| Active | 1 [Reference] | 1 [Reference] |
| Insufficient activity | 1.2 (1.2-1.3) | 1.0 (1.0-1.1) |
| Inactive | 2.0 (1.9-2.1) | 1.3 (1.2-1.3) |
Abbreviations: OR, odds ratio; CI, confidence interval; PA, physical activity.
Because the education and income variables were not correlated (Pearson r = 0.0536), the final model used to derive the adjusted values consisted of all independent covariates and the interaction between education and income; all predictors were simultaneously entered into the model (P = .047).
PA categories were based on the Surgeon General's recommendations (17). "Active" was defined as meeting the recommendations (30 minutes or more of moderate-intensity PA on 5 or more days per week or 20 minutes or more of vigorous-intensity PA on 3 or more days per week) during the preceding month, "insufficient activity" was defined as not meeting the recommendations during the preceding month, and "inactive" was defined as reporting no PA outside of one's occupation during the preceding month.